Experimental Study on Time-Dependent Pumping Behaviour of 3D Concrete Printing (2025-06)¶

3D concrete printing (3DCP) is a novel automated construction technology that offers a variety of structural, environmental and economic benefits compared to traditional construction methods. 3DCP requires a stiff consistency in its fresh state to facilitate the stability of the printed layers. This is traditionally achieved by adding buildability enhancing additives at the initial mixing. However, incorporating higher dosages of buildability enhancing additive in concrete may give rise to concerns at the pumping stage such as high pumping pressure requirements and possible blockages inside the pipeline, specially at prolonged resting durations of the concrete. Therefore, a proper understanding of the time-dependent behaviour of concrete rheology and flow mechanism of 3D printable concrete at the pumping stage is essential to facilitate a smooth pumping operation. Therefore, this study investigates the rheology and flow behaviour of 3D printable concrete with varying resting durations. For this purpose, a laboratory scale pumping setup was established with a 6m long horizontal pipeline. Concrete was pumped in pre-defined resting periods and the pumping pressure was recorded. The rheological properties of bulk concrete and lubrication layer (LL) were obtained experimentally and f ina the applicability of different analytical pumping pressure prediction equations, i.e. Kaplan’s equation and Buckingham-Reiner equation were evaluated. The comparison between experimental and predicted values suggests a gradual transition in concrete flow behaviour from plug flow, where shearing takes place only in LL, to a more homogeneous flow state where the shearing of concrete governs the pumpability.